There exist a large number of electromagnetic injection valves for the purpose of fuel injection into the suction pipe of combustion motors. A common characteristic for these injection valves is a desire for high dosage accuracies. Such high dosage accuracies can be achieved only with very short opening and closing times. Opening and closing times for the best known valves are 0.5-1.5 ms, depending somewhat on the impedance of the electromagnet. The required short closing times should be achieved with the lowest possible input of electrical energy.
State of the art valves typically are of axially symmetric design. The armature of such valves is located at the central axis of the valve and acts on a valve obturator which in most cases is of needle-type design. The outside diameter of these valves is in general 20-25 mm Magnetic return flow usually is by means of a massive metallic housing which provides the base for both the magnetic pole and the valve seat. This housing must be precision made to prevent unacceptable dislocations of the magnetic pole. Usually this results in a series of narrowly defined precision tolerance limits which are difficult to achieve in production, or it is necessary to select component parts which fit precisely to each other. In order to prevent objectionable armature bounce, and in order to achieve short floating times, the conventional injectors feature only very small stroke heights. Stroke heights of modern injector valves are in the range of 0.05-0.1 mm. In order to prevent unacceptable variations in flow-through characteristics, the state of the art valves require extremely tight machining tolerances. In addition, state of the art valves require a difficult calibration procedure.